Endpoint determination for capillary-assisted flow control

ABSTRACT

Apparatus and method for determining endpoint of a fluid supply vessel in which fluid flow is controlled through a flow passage disposed in an interior volume of the fluid supply vessel with a static flow restricting device and a selectively actuatable valve element upon establishing fluid flow. The endpoint determination can be employed to terminate fluid supply from the fluid supply vessel and/or to switch from a fluid-depleted supply vessel to a fresh vessel for continuity or renewal of fluid supply operation. The apparatus and method are suitable for use with fluidutilizing apparatus such as ion implanters.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a national phase under 35 USC 371 of International PatentApplication PCT/US 2011/041013 filed Jun. 18, 2011 in the names ofJoseph D Sweeney, et al., which in turn claims the benefit of priorityunder 35 USC 119 of U.S. Provisional Patent Application No. 61/356,451filed Jun. 18, 2010 and U.S. Provisional Patent Application No.61/366,523 filed Jul. 21, 2010. The disclosures of International PatentApplication PCT/US 2011/041013 and of U.S. Provisional PatentApplication No. 61/356,451 and U.S. Provisional Patent Application No.61/366,523 are hereby incorporated herein by reference in theirrespective entireties, for all purposes.

FIELD

The present disclosure relates to endpoint determination forcapillary-assisted flow control, e.g., in delivery of semiconductormanufacturing fluid from a source of same to a semiconductormanufacturing tool.

DESCRIPTION OF THE RELATED ART

In the use of fluid supply vessels, the supplied fluid may be utilizedin apparatus or operations in which continuity of operation is essentialto their economic character.

As an example, dopant fluids may be supplied to ion implant tools insemiconductor manufacturing facilities. Any sudden unanticipatedexhaustion of the dopant fluid supply during tool operation will forceshutdown of the implant tool, and require discarding or rework of wafersthen in process, as well as delay in operation as a fresh fluid supplyvessel is installed to replace the fluid-depleted vessel.

Such sudden unanticipated exhaustion of the fluid supply and theoperational dislocations attending same pose a severe economicdisadvantage to the process system. This problem is relevant to the useof fluid supply vessels employing capillary-assisted flow control of thesupplied fluid.

SUMMARY

The present disclosure relates to endpoint determination forcapillary-assisted flow control.

In one aspect, the disclosure relates to a method of determining anendpoint of a fluid supply process, the method comprising:

-   selectively establishing fluid flow from a fluid supply vessel;-   controlling fluid flow through a flow passage disposed in an    interior volume of the fluid supply vessel with a static flow    restricting device and a selectively actuatable valve element upon    establishing fluid flow; and-   monitoring at least one characteristic of the fluid supply vessel or    a fluid dispensed therefrom to determine the endpoint,-   wherein the static flow restricting device and the selectively    actuatable valve element are arranged along the flow passage.

In another aspect, the disclosure relates to an endpoint monitoring andcontrol apparatus for a fluid supply vessel in which fluid flow iscontrolled through a flow passage disposed in an interior volume of thefluid supply vessel with a static flow restricting device and aselectively actuatable valve element upon establishing fluid flow. Theendpoint monitoring and control apparatus comprises a monitoring unitadapted to monitor at least one characteristic of the fluid supplyvessel or a fluid supplied therefrom and to generate an output signal,and a CPU operatively linked in output signal receiving relationship tothe monitoring unit. The CPU has stored therein endpoint conditioninformation and responsive in receipt of an output signal from themonitoring unit indicative of the endpoint condition to generate acontrol signal for use in terminating fluid supply from the fluid supplyvessel.

An additional aspect of the disclosure relates to a fluid-utilizingapparatus adapted to perform the method of the disclosure as broadlydescribed above.

A still further aspect of the disclosure relates to a method as broadlydescribed above, wherein the method is performed by a fluid-utilizingapparatus.

In another aspect, the disclosure relates to the endpoint monitoring andcontrol apparatus described above, as operationally arranged with atleast one fluid supply vessel.

A further aspect of the invention relates to a fluid supply system,comprising a fluid supply vessel having an interior volume for holdingfluid, first flow circuitry in the interior volume arranged to controlflow of fluid during supply of fluid from the vessel, said first flowcircuitry including a static flow restricting device and a selectivelyactuatable valve element, and a second flow circuitry coupled with thevessel for discharging fluid therefrom, wherein the system comprises atleast one of the following elements:

-   (i) a buffering reservoir in the interior volume of the vessel,    coupled with the first flow circuitry, arranged to hold fluid for    buffering release thereof to the first flow circuitry;-   (ii) a buffering reservoir exterior of the vessel, coupled with the    second flow circuitry, arranged to hold fluid for buffering release    thereof to the second flow circuitry;-   (iii) a pressure regulator arranged to regulate fluid pressure in    the second flow circuitry;-   (iv) a pressure transducer arranged to monitor fluid pressure in the    second flow circuitry; and-   (v) a mass flow controller arranged to control mass flow of fluid in    the second flow circuitry, wherein when any one or more of elements    (ii)-(v) is comprised in said system, the system may further    optionally comprise a CPU programmably arranged to receive at least    one monitoring signal from a device monitoring at least one    characteristic of the fluid supply vessel or a fluid dispensed    therefrom, to determine an endpoint of fluid supply from the fluid    supply vessel.

Other aspects, features and embodiments of the invention will be morefully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of delivery pressure, in ton, and flow rate, in sccm,each as a function of time, in hours, for a simulated fluid supplyvessel holding boron trifluoride gas, with a capillary restrictiondevice in the interior volume of the supply vessel, upstream of a vacuumactuated valve in such interior volume, with the supply vessel having avalve head coupled to its neck portion, for opening or closing of avalve element in such valve head, to enable flow of fluid or toterminate flow of fluid, respectively.

FIG. 2 is a schematic representation of an illustrative fluid supply andutilization system in which the monitoring and control arrangements ofthe present disclosure may be advantageously implemented for endpointdetermination and operational management of fluid supply vessels.

FIG. 3 is a schematic representation of a fluid supply and utilizationsystem according to another implementation in which the end pointdetermination can be made using proportional-integral-derivative (PID)output of a mass flow controller, with augmentation of the fluid supplyby buffering reservoirs to accommodate sudden onset pressure diminutionat the endpoint condition.

FIG. 4 is a graph of delivery pressure as a function of time, for anillustrative fluid supply vessel utilizing capillary-assisted flowcontrol, in which the graph shows the gradual increase and sudden onsetdrop in delivery pressure of the fluid being supplied as the vesselreaches an endpoint condition.

DETAILED DESCRIPTION

The present disclosure relates to endpoint determination forcapillary-assisted flow control, such as may be used for supplying fluidto a semiconductor manufacturing tool such as an ion implanter.

The endpoint determination may be carried out in a method including:selectively establishing fluid flow from a fluid supply vessel;controlling fluid flow through a flow passage disposed in an interiorvolume of the fluid supply vessel with a static flow restricting device,e.g., a capillary device, and a selectively actuatable valve elementupon establishing fluid flow; and monitoring a characteristic of thefluid supply vessel or a fluid supplied therefrom to determine theendpoint, wherein the static flow restricting device and the selectivelyactuatable valve element are arranged along the flow passage.

The static flow restricting device may comprise one or more capillarytype or flow throttling passages. For example, the flow restrictingdevice can include two or more capillary type or flow throttlingpassages arranged in parallel along a portion of the flow passage.

The static flow restricting device can be positioned in the interiorvolume of the supply vessel in any suitable manner and/or configuration.The static flow restricting device can for instance be positioned beforeor after the selectively actuatable valve element on the flow passage.In one illustrative arrangement, the static flow restricting device ispositioned between the selectively actuatable valve element and an inletof the flow passage. In another illustrative arrangement, theselectively actuatable valve element is positioned between the staticflow restricting device and an inlet of the flow passage.

The selectively actuatable valve element can be of any suitable type.For example, the selectively actuatable valve element can comprise avacuum actuated valve. In one specific embodiment, the selectivelyactuatable valve element comprises a poppet type valve.

The fluid contained in and supplied from the fluid supply vessel can beof any suitable type. For example, the fluid can comprise a fluid havingutility in semiconductor manufacturing operations, such as chemicalvapor deposition, etching operations, atomic layer deposition,lithography operations, and ion implantation. More specifically, thefluid can comprise a fluid species selected from the group consisting ofarsine, phosphine, boron trifluoride, boron trichloride, diborontetrafluoride, diborane, hydrogen selenide, xenon difluoride, silane,polyalkylsilanes, organometallic reagents, fluorine (F2), hydrogensulfide (H2S), germane (GeH4), and hydrido and alkylhydrido species ofSi, Ge, Sn and Sb.

In the endpoint determination method, a characteristic of the fluidsupply vessel or a fluid supplied therefrom is monitored to determinethe endpoint. Such monitoring may be conducted in any suitable manner.In various embodiments, the monitoring includes comparing the monitoredcharacteristic to a reference characteristic to determine the endpoint.

The monitored characteristic itself can be of any useful type and canfor example include physical characteristics, temporal characteristics,hydrodynamic conditions, or any other qualities, quantities, features orstates. The monitored characteristic in specific implementations of theendpoint determination may include one or more appropriate monitoringvariables, such as fluid flow duration, fluid flow rate, fluid pressure,fluid temperature, supply vessel temperature, supply vessel weight,concentration of a component of the supplied fluid, etc.

For example, the endpoint can be determined to have been reached when:a) a predetermined fluid flow rate has been detected; b) a predeterminedfluid pressure has been detected; c) a predetermined fluid flow durationhas been detected; d) a predetermined amount of fluid has been supplied;e) a predetermined change in fluid pressure has been detected; f) apredetermined change in fluid flow rate has been detected; and/or g) apredetermined weight or change of weight of the supply vessel and itscontents has been detected.

In instances in which the fluid supply is arranged to determine endpointwhen a predetermined fluid flow rate has been detected, the endpointfluid flow rate in a specific embodiment may be within a range of from0.1 to 5 standard cubic centimeters per minute (sccm). The user mayconfigure the fluid supply monitoring arrangement to determine endpointat a value that is a predetermined percentage of the desired flow ratesetpoint for normal dispensing operation of the supply vessel, or thatis in a specified ratio to such desired flow rate setpoint for normaldispensing operation.

In applications in which the fluid supply is arranged to determineendpoint when a predetermined fluid pressure has been detected, theendpoint condition can be any suitable pressure level, e.g., a pressurevalue in a range of from 0 to 760 ton, or a pressure in a range of from2 to 400 ton, or any other suitable value of pressure of the fluidsupplied from the vessel.

In applications in which the fluid supply is arranged to determineendpoint when a predetermined fluid flow duration has been detected, theendpoint duration can be defined by the average user flow rate andvessel inventory. For example, a supply vessel containing 300 grams ofboron trifluoride, supplying BF₃ gas at an average flow rate of 3 sccm,could theoretically supply gas for about 549 hours, assuming delivery of100% of the gas inventory in the vessel. In this case, the user mightselect the endpoint to be 75%, 80%, 85%, or an even higher percentage ofthis value. In a specific embodiment, such endpoint value might beselected to be 80%, or 440 hrs, at which time the user might receive analarm or message indicating that the supply vessel is near empty. Theactual percentage that the user selects is likely to be dependent on theuser's knowledge of the supply vessel heel (heel being the amount ofresidual fluid remaining in the vessel at the conclusion of discharge offluid from the vessel, when run to a point at which the pressure offluid from the vessel is no longer adequate to overcome pressure drop inthe flow circuitry interconnecting the vessel with a fluid-utilizingapparatus or location, so that flow stops), or otherwise based on priorexperience with the duration of fluid discharged until endpointconditions are achieved. Alternatively, the duration endpoint can beestablished empirically, by charging the supply vessel with fluid to apredetermined extent, and then logging the duration of the fluiddischarge at various rates of discharge, to establish a referencedatabase of endpoint conditions that can be programmatically employed toset endpoint alarm conditions.

In applications in which the fluid supply is arranged to determineendpoint when a predetermined cumulative weight of fluid is dischargedfrom the supply vessel, the predetermined endpoint value can be selectedbased on knowledge of the supply vessel heel or prior experience withsupply vessels of the same character, or otherwise empirically. By wayof example, for a supply vessel containing 335 grams of fluid to beselectively discharged for use, the heel might be about 44 grams (for a3 sccm flow rate), and the endpoint might be chosen as being acumulative weight value in a range of 250-300 grams of discharged fluid.This cumulative value will depend on the fill level of the vessel whenfurnished for fluid supply service as a “fresh” vessel, and can bereadily established for varied levels of fill of the fluid in the supplyvessel. Measurement and monitoring of the weight of fluid dischargedfrom the supply vessel can be carried out by continuous measurement ofthe supply vessel weight, from the initial full state as discharge offluid proceeds, or by monitoring vessel weight continuously after somepoint in the service life of the vessel, when intermittently takenweight data indicates a suitable point as having been reached, e.g., at80% of initial fluid inventory as having been discharged from thevessel.

Other techniques for monitoring the weight of the fluid discharged fromthe supply vessel to establish an endpoint condition can include use ofa mass flow controller in order to totalize the flow of the dischargedfluid over time, and computationally using the totalized value with themolecular weight of the discharged fluid to determine the weight of thefluid that has been released from the supply vessel.

In applications in which the endpoint is determined to have been reachedwhen a predetermined change in fluid pressure has been detected, theendpoint can be established as a specific percentage or fraction of thedelivery pressure. For example, using a supply vessel having a deliverypressure of from 200 to 400 torr, an endpoint value in specificembodiments may be 10%, 20%, 30%, 50% or more of such delivery pressure.

In applications in which the endpoint is determined to have been reachedwhen a predetermined change in fluid flow rate has been detected, thevariation from a set point fluid discharge rate from the supply vesselcan be employed as the endpoint marker, at a selected value. Thisvariation can depend on the specific fluid-utilization apparatus orlocation of use of the fluid discharged from the supply vessel. In aspecific embodiment, the variation indicative of the endpoint beingreached can be any suitable value, e.g., a fluid flow rate change of 1%,3%, 5%, 10%, etc.

In applications in which the endpoint is determined to have been reachedwhen a predetermined weight or change of weight of the fluid supplyvessel has occurred, the weight of the vessel can be monitored duringthe discharge of fluid for use, or during a relevant portion of suchdischarge, to determine when the endpoint condition has been reached.

In various embodiments in which the fluid supply vessel is used toprovide fluid to an ion implanter in a semiconductor manufacturingfacility, endpoint may be determined by monitoring implanter beamcurrent or ion source arc current in the implanter to detect a drop insuch current levels, as being indicative of the fluid supply vesselapproaching an empty state. In order to improve the accuracy andreliability of the monitoring operation, such current monitoringoperation may be combined with one or more of the monitoring techniquesdescribed in the preceding discussion.

More generally, any of the aforementioned techniques or monitoringmodalities can be employed in combination with one or more others, toprovide a combinatorial monitoring system to provide redundancy ofmonitoring capability, or to provide multiple inputs to a monitoringsystem, to enhance accuracy and reliability of such monitoring. Forexample, an endpoint monitoring and control system may be provided,enabling a user to select a desired type or types of endpoint monitoringcapability from among multiple provided modalities. Thus, a user mayselect a percentage drop in delivery pressure of supplied fluid as themonitored variable for endpoint determination, and select an actualvalue to be employed as the endpoint determinant, e.g., a 20% drop indelivery pressure. The user may additionally, or alternatively selectmultiple variables for monitoring, e.g., percentage drop in fluiddelivery pressure of fluid discharged from the vessel and total numberof grams of fluid discharged from the vessel.

The aforementioned monitored variables for endpoint determination may bedetected by any suitable sensors, detectors, or monitors that areappropriate to such purpose. The monitoring apparatus may be arranged toprovide an output signal that is indicative or correlative of themonitored condition or state of interest, with the output signal of suchmonitoring apparatus being transmitted by suitable signal transmissionlines to a central processor unit (CPU) for processing of suchmonitoring signal and responsive generation of an output control signalindicative of the endpoint that may be used to actuate an endpoint alarmand/or apparatus that effects shutdown or isolation of thefluid-depleted supply vessel, so that it is taken off line forreplacement with a fresh supply vessel, for continued or renewedoperation involving fluid supply. The apparatus actuated by such outputcontrol signal can in specific embodiments be flow control valves orvalve actuators, power supplies, pumps, compressors, purge apparatus, orany other suitable apparatus that is controlled or controllable by theoutput signal. The CPU employed in such monitoring and control systemscan be of any suitable type, including for example special purposeprogrammed or programmable computers, microprocessors, programmablelogic controllers, etc.

In specific illustrative embodiments of the monitoring methodology ofthe present disclosure, the endpoint condition may be selected so thatat such condition, a specified amount of the original fluid inventory ofthe fluid supply vessel is present in the interior volume of the vessel,e.g., an amount in a range of from 1 to 20% of the original fluidinventory, such as 1%, 2%, 5%, 8%, 10%, 12%, 15% or 20%, or other valueor value in other ranges.

When pressure is used as a monitored variable for endpoint monitoringpurposes, the pressure can be monitored in any suitable manner, e.g., bymonitoring pressure drop across the static flow restricting device thatis disposed in the interior volume of the supply vessel, and/or bymonitoring pressure drop across a static flow restricting device in thefluid flow circuitry coupled with the fluid supply vessel to deliverfluid to the point of use, such as a restricted flow orifice (RFO), aninline gas snubber device, or other suitable device in or coupled withthe flow circuitry.

While the foregoing is directed primarily to ion implantationapplications, in respect of specific parameters and ranges applicable toendpoint values, those skilled in the art can readily empiricallydetermine appropriate settings and operational parameters, based on thepresent disclosure, applicable to other applications.

The static flow restricting device that is disposed in the interiorvolume of the supply vessel can be of any appropriate type, and can forexample comprise one or more capillary tubes, through which fluid isflowed for ultimate discharge from the fluid supply vessel. Aspreviously discussed herein, the static flow restricting device in theinterior volume of the supply vessel is employed to control fluid flowthrough a flow passage in such interior volume, in conjunction with aselectively actuatable valve element upon establishing fluid flow. Inone embodiment, the static flow restricting device comprises two or morecapillary type or flow throttling passages arranged in parallel along aportion of the flow passage.

Concerning pressure drop across a capillary tube, in a given capillarytype flow restricting device, the design of such device, including thenumber, length and diameter of capillary tubes, the fluid flow rate ofthe fluid discharged from the supply vessel, the temperature and thesupply vessel pressure at any specific moment in time, will all effectthe pressure drop. The pressure drop associated with endpoint status ofthe fluid supply vessel may be mathematically determined as hereinafterdescribed, to specify a particular pressure drop that is associated witha specific fractional or percentage loss of delivery pressure, or lossof a specific fractional or percentage amount of the set point orotherwise desired flow rate of the fluid discharged from the supplyvessel for use.

The capillary type flow restricting device in various embodiments may bepositioned upstream of a regulator, vacuum actuated check valve, orother flow modulating device in the interior volume of the fluid supplyvessel.

The endpoint profile of a capillary and regulator system can be modeledto show the pressure and flow profile. The present applicants haveexperimentally confirmed these results by building a capillary andregulator system. At the end point of the gas supply vessel, thepressure drop that is associated with frictional losses is significantand therefore the density can no longer be assumed to be constant. Thisresults in having compressible fluid flow. In this case the followingequation (1) can be used to estimate flow.

More specifically, the mathematical determination of pressure drop of acapillary tube may comprise determination based on a pressure dropequation (1), as set out below:

$\begin{matrix}{{p_{1}^{2} - p_{2}^{2}} = {G^{2}{\frac{R\; T}{M_{w}}\left\lbrack {\frac{4{fL}}{D} + {2\;{\ln\left( \frac{p_{1}}{p_{2}} \right)}}} \right\rbrack}}} & (1)\end{matrix}$wherein the equation variables are as defined below:

-   p₁=conduit inlet pressure-   p₂=conduit outlet pressure-   G=mass flux of gas-   R=universal gas constant-   T=gas temperature-   M_(w)=gas molecular weight-   f=friction factor=16/RE (laminar flow)-   RE=Reynolds number=GD/μ-   μ=gas viscosity-   L=conduit length-   D=conduit diameter

FIG. 1 is a graph of delivery pressure, in ton, and flow rate, in sccm,each as a function of time, in hours, for a simulated fluid supplyvessel holding boron trifluoride gas, with a capillary restrictiondevice in the interior volume of the supply vessel, upstream of a vacuumactuated valve in such interior volume, with the supply vessel having avalve head coupled to its neck portion, for opening or closing of avalve element in such valve head, to enable flow of fluid or toterminate flow of fluid, respectively. The valve head may be arrangedfor manual or automatic operation of the valve element in the valvehead, such as by a hand wheel for manual operation, or a pneumatic valveactuator for automatic operation, or in some other arrangement enablingtranslation of the valve element in the valve head, between fully openedand fully closed positions.

In the simulated fluid supply vessel for which the FIG. 1 graph wasgenerated, the capillary restriction device comprises an array of sevencapillary tubes, each 2.8 inches in length and 20 μm in internaldiameter. The fluid flow rate for the boron trifluoride gas is 3 sccm.

At time zero on the FIG. 1 graph, the supply vessel has been inoperation, discharging fluid for downstream utilization, for a number ofhours in steady-state fluid supply operation. The delivery pressureshown in the graph is the pressure of the fluid when it is dischargedfrom the vessel. The pressure p₂ in equation (1) is the pressureimmediately downstream of the capillary flow restrictor. When pressurep₂ declines to the supply vessel delivery pressure set point, denotedhere as p₃, the two pressures thereafter will be substantially equal toone another for the remainder of the fluid supply service life of thefluid supply vessel in steady-state fluid discharge operation. Thefollowing is a description of fluid discharging operation of such fluidsupply vessel.

In fluid discharging operation, fluid is discharged from the supplyvessel for number of hours, depending on the initially provided fluidinventory (fill quantity) and flow rate set point. As fluid isprogressively discharged from the supply vessel, the vessel pressure,p₁, is dropping. For a given flow rate of fluid, as well as a giventemperature and capillary restrictor design, the right-hand side ofequation (1) is substantially constant for all p₁ and p₂ values, the Lnterm being very small in relation to the 4 fL/D term of the equation. Asa result, the left-hand side term must remain substantially constant forany given fluid flow rate G.

Thus, p₁{circumflex over (0)}2−p₂{circumflex over (0)}2=C (constant),or, algebraically, (p₁{circumflex over (0)}2−p₂{circumflex over(0)}2)=(p₁+p₂)*(p₁−p₂)=C. As p₁ declines, p₂ also declines, but in orderto ensure that the equation is satisfied, i.e., that (p₁+p₂)*(p₁−p₂)=C,the term (p₁−p₂) must increase. In consequence, p₂ must decline morerapidly than p₁. Accordingly, delivery pressure in supply vessels havingcapillary type flow restrictors therein will drop rapidly as deliverypressure approaches zero, and there is relatively short time to respond.Differentiation of the pressure drop expression shows that p₂ changeswith respect to p₁ in the following way:dp ₂ /dp ₁ =p ₁ /p ₂so that as p₂ gets small and eventually is equal to and then less thanthe set point of the internal flow control device, e.g., regulator orvacuum actuated check valve, the change in p₂ with respect to p₁ becomeslarger and larger. In other words, the drop in delivery pressureaccelerates with a drop in supply vessel pressure. This results in thedelivery pressure of the discharge fluid changing from a desireddispensing pressure level to a value very close to zero in a very shortperiod of time.

Once the delivery pressure drops to a particular low value, e.g., 3-10torr, or other low pressure that is just adequate to drive the flow ofdischarged fluid through the discharge flow circuitry, the flow rate ofdischarged fluid will gradually start to fall, as the supply vesselpressure is dropping with depletion of gas therefrom. Now the flow rateG will start to drop in accordance with equation (1) above, but with p₂approximately constant (p₂ will drop very slightly with flow, as a lowerflow requires a lower pressure to drive the fluid through the dischargeflow circuitry. The flow then continues to drop until the user of thefluid supply vessel notices, or until the downstream fluid-utilizingapparatus shuts down and/or alarms by action of an interlock assembly.For example, when the downstream fluid-utilizing apparatus is an ionimplanter receiving dopant source gas from the fluid supply vessel, theinterlock mechanism may be actuated by specific loss of flow rate orbeam current.

The fluid supply vessel monitoring methods and systems of the presentdisclosure enable such extremely rapid transition from fluid dischargingoperation to exhaustion of the supply vessel to be avoided, by endpointdetermination, and controlled cessation of discharge operation as aresult of one or more monitored variables affecting and/or affected bythe fluid discharge operation. The monitoring may as previouslydescribed be associated with a CPU and/or other control device(s) thatmay have stored in a memory or memory element of the CPU a fluiddischarge operational profile for the monitored variable(s), as abaseline profile from which actual monitoring data can be assessed fordeviations that indicate onset or achievement of a predeterminedfluid-depleted state of the fluid supply vessel, and thus trigger endpoint actuation or de-actuation of control devices to terminatedischarge of fluid from the fluid supply vessel. The CPU thus may beprogrammatically arranged for such monitoring, and to output one or morecontrol signals to effect end point operational changes to shut down orisolate the fluid supply vessel, and/or to effect change over to a freshfluid supply vessel containing the fluid for further operation of thefluid-utilizing apparatus or locus.

Thus the present disclosure contemplates, in one aspect, an endpointmonitoring and control apparatus for a fluid supply vessel in whichfluid flow is controlled through a flow passage disposed in an interiorvolume of the fluid supply vessel with a static flow restricting deviceand a selectively actuatable valve element upon establishing fluid flow.Such endpoint monitoring and control apparatus comprises a monitoringunit adapted to monitor at least one characteristic of the fluid supplyvessel or a fluid supplied therefrom and to generate an output signal,and a CPU operatively linked in output signal receiving relationship tothe monitoring unit, said CPU having stored therein endpoint conditioninformation and responsive in receipt of an output signal from themonitoring unit indicative of the endpoint condition to generate acontrol signal for use in terminating fluid supply from the fluid supplyvessel.

The endpoint monitoring and control apparatus may further comprise acontrol device operatively linked in control signal receivingrelationship to the CPU and responsive in receipt of the control signalto operate and terminate or assisting to terminate fluid supply from thefluid supply vessel. Such endpoint monitoring and control apparatus thusmay be operationally arranged with at least one fluid supply vessel, formonitoring and control of the operation of such fluid supply vessel oran array of multiple fluid supply vessels. In a specific embodiment, theendpoint condition information stored in the CPU may comprise at leastone fluid discharge operational profile for a monitored characteristicof the fluid supply vessel, as a baseline profile from which actualmonitoring data can be computationally assessed by the CPU fordeviations that indicate onset or achievement of a predeterminedfluid-depleted state of the fluid supply vessel.

As another variation of the fluid supply arrangements that may beemployed within the broad scope of the disclosure hereof, the fluidsupply vessel and/or downstream flow circuitry may be arranged with oneor more buffer volumes for accumulation of fluid to be discharged to thefluid-utilizing apparatus or locus, so that one or more reservoirs ofsuch fluid is provided to enable continued dispensing of fluid atdesired set point conditions, beyond what would be possible in theabsence of such reservoir(s). The fluid supply system including suchreservoir(s), as buffer zones within or outside of the supply vessel,can thereby extend the operational lifetime of the fluid supply vessel,and can be arranged so that such additional supply of fluid continuesbeyond the endpoint that would otherwise trigger shutdown or switch overto her fresh vessel, so that transitional time is afforded for theoperational changes incident to endpoint arrival of the fluid supplyvessel.

The static flow restricting device in the interior volume of the fluidsupply vessel, as mentioned, can be of any suitable type. In oneembodiment, the flow restricting device can comprise a restricted floworifice (RFO), and such RFO can be positioned in the discharge path offluid in the interior volume of the vessel, upstream or downstream of aninterior flow-modulating device such as a regulator or vacuum actuateddispensing check valve. For example, the fluid supply vessel may includemultiple RFO devices and/or multiple regulators, in embodimentsincluding RFO and regulator components for flow control of the fluidthat is discharged from the vessel in use.

In another aspect, the endpoint of the fluid supply vessel in operationcan be determined, and/or fluid inventory of the fluid supply vessel canbe monitored, by measuring a change in a property or properties of thefluid supply vessel or a component thereof. Suitable properties for suchapplication include, without limitation, acoustic, thermal, resistiveand/or pressure chromic properties. In various applications, materialscan be integrated in the fluid supply vessel wall or a component of thevessel, which are useful for sensing/measuring one or more properties ofthe vessel.

For example, the wall of the fluid supply vessel may be thermally probedat vertically spaced-apart locations and the resulting thermal responsemeasured, e.g., in applications in which a liquid inventory ismaintained in the interior volume of the fluid supply vessel. Since apredetermined heat input at a portion of the wall bounded by gas in thevessel interior will be dissipated very differently that wall portionsthat is in internal contact with liquid, heat above a liquid interfacewill be dissipated more slowly (because gas is a poor conductor), whilethe same input at the wall below the liquid interface will dissipatemuch more rapidly due to the thermal conductivity of the liquid.

The monitoring will thus move down the wall is liquid inventory isexhausted, and the liquid interface can be tracked quite closely at anygiven point in time during the gas discharging operation.

In another arrangement, one sensor is located on the exterior wall ofthe fluid supply vessel, at a level corresponding to a desired heels forchange-out. The fluid supply vessel monitoring and control system isarranged to monitor repetitive heat inputs (periodic inputting of heat)at that input site, and when liquid is depleted to place the wall on theother side of the thermal input/monitoring locus in contact with gas,the monitoring signal will change to reflect gas rather than liquid atthat site. The signal can trigger (through an optical cable, or othersignal transition modality) a change out operation, to minimizedown-time of the tool. Rather than a thermal challenge (input) for themonitoring, any other external wall input and monitoring capabilitycould be used, such as acoustic, vibratory, ultrasound, or other input,where the input can propagate to/through the fluid supply vessel wall,and produce a differential response depending on whether gas or liquidis contacting the interior surface of the vessel at the signalinput/monitoring site.

The present disclosure contemplates a fluid-utilizing apparatus that isadapted to perform the broad method of the invention, as well as amethod of such type, wherein the method is performed by afluid-utilizing apparatus.

FIG. 2 is a schematic representation of an illustrative fluid supply andutilization system 10 in which the monitoring and control arrangementsof the present disclosure may be advantageously implemented for endpointdetermination and operational management of fluid supply vessels, suchas the vessels 12 and 14 shown in the drawing.

In FIG. 2, the fluid supply vessel 12 is shown as the onstream vessel,and fluid supply vessel 14 is shown as being off stream, such off streamstatus being indicated by the dashed line representation of respectivefluid supply and control signal transmission lines 16 and 18. Theonstream vessel 12 as illustrated includes a casing or shell 20enclosing an interior volume 22, in which is disposed a static flowrestricting device 24, e.g., comprising an array of capillary tubesarranged in parallel to one another, through which fluid from theinterior volume 22 can flow along a flow path including the static flowrestricting device 24, flow modulating device 26, e.g., a vacuumactuated dispensing check valve, and discharge conduit 28. The dischargeconduit 28 delivers fluid to valve head 30 containing a valve elementthat is translatable between fully open and fully closed valve positionsby the automatic valve actuator 32, which is operated by control signalstransmitted in signal transmission line 34 to such actuator from the CPU36.

The valve head 30 of the vessel 12 includes a discharge port coupled tofluid discharge line 40 through which fluid is flowed to the downstreamfluid utilizing facility 42, which may for example comprise an ionimplanter of a semiconductor manufacturing facility. In the fluidutilizing facility, the fluid supplied from fluid discharge line 40 isutilized, and in the specific embodiment shown, the fluid utilizationoperation in facility 42 produces an effluent that is discharged ineffluent discharge line 44. The discharged effluent flows in dischargeline 44 two effluent treatment unit 46, from which treated effluent isdischarged in vent line 48.

In the discharge line 42 which fluid is supplied from the fluid supplyvessel 12, a discharge fluid monitoring unit 50 is disposed, to monitoran endpoint-determinative characteristic of the discharged gas flowingtherethrough. The discharge fluid monitoring unit 50 is constructed andarranged to generate an output signal that is correlative of thecharacteristic being monitored, and such output signal is transmitted insignal transmission line 52 to the CPU 36 for processing. Also disposedin discharge line 40 is a flow control valve 54 coupled in controlledrelationship by control signal transmission line 56 to CPU 36, and inthe specific illustrated embodiment, a further flow control device 60.The further flow control device 60 can be of any suitable type, and mayfor example comprise a mass flow controller, pressure regulator, orother appropriate device. Such further flow control device mayadditionally be coupled with CPU 36 (connection not shown in FIG. 2).

The fluid monitoring unit 50 may be arranged to monitor pressure of thedischarged fluid flowing through discharge line 40, and to transmit apressure-correlative output signal to the CPU 36. In lieu of suchpressure monitoring, the monitoring unit 50 may monitor any othersuitable characteristic of the dispensed fluid, such as temperature,flow rate, concentration of a gas species in a multicomponent gasmixture when the dispensed fluid comprises for example a carrier gas andan active gas, or any other arrangement in which the monitoring unit 50is specifically adapted for such specific monitoring application. Themonitored characteristic may therefore be detected intermittently orcontinuously, or a combination thereof, to identify conditionsindicative of onset of exhaustion of the fluid supply vessel, andtransmit an output signal to the CPU to effectuate correspondingtransition of the fluid supply and utilization system.

In the FIG. 2 arrangement, when the endpoint-associated condition isdetected by the monitoring unit 50, the corresponding signal transmittedto the CPU 36 in signal transmission line 52 is processed by the CPU andan output produced. Such output comprises a control signal in the FIG. 2embodiment, with a signal being transmitted in signal transmission line34 to actuator 32 to close the valve and valve head 30, and concurrentlya control signal is transmitted in signal transmission line 56 to flowcontrol valve 54, to shut such valve, so that the exhausted vessel 12can be taken off-line. In connection with such transition, the fluidsupply vessel 14 may be switched into operation, with transmission ofthe control signal in signal transmission line 18 to valve actuator 64arranged to control the valve in valve head 66, so that fluid from fluidsupply vessel 14 is flowed from a discharge port 68 of the valve head 66through fluid discharge lines 16 to fluid discharge line 40 (vessel 12being uncoupled from discharge line 40 at such point), for continuity orrenewal of fluid flow to the fluid utilizing facility 42.

The fluid supply vessel 14 as shown includes a casing or shell 70enclosing an interior volume of 72 of the vessel. In the interior volume72 is disposed a discharge conduit 74 containing a filter 76, arestricted flow orifice 78 and a flow control device 80 therein. Theflow control device 80 may comprise a pressure regulator, a vacuumactuated dispensing check valve, or any other suitable flow controldevice useful for modulating flow of fluid dispensed from the vessel.

Although not shown for reasons of simplicity, the respective vessels 12and 14 can be integrated into a valve manifold arrangement to facilitateswitching and changeover of operation, from a depleted vessel to a freshvessel, wherein valving in the manifold is suitably arranged to enablechange out of depleted vessels, while maintaining continuity ofoperation. Such valving may therefore be operatively controlled by a CPUsuch as CPU 36 shown in the schematic drawing in FIG. 2, or in otherappropriate manner.

It will be recognized that the fluid supply and utilization system maybe variously configured, within the skill of the art, based on thedisclosure herein, to encompass other aspects, features and embodiments.For example, instead of the two fluid supply vessels 12 and 14, morethan two vessels can be employed, or only a single vessel may beemployed in the system. The monitoring and control elements and theirarrangement may be widely varied, to provide active tracking of thefluid dispensing operation, with respect to determination of endpoint,and responsive action to manage the fluid utilizing operation beingcarried out.

FIG. 3 is a schematic representation of a fluid supply and utilizationsystem 110 according to another implementation, in which the end pointdetermination can be made using proportional-integral-derivative (PID)output of a mass flow controller, with augmentation of the fluid supplyby buffering reservoirs to accommodate sudden onset pressure diminutionat the endpoint condition.

As illustrated in FIG. 3, the fluid supply and utilization system 110includes a fluid supply vessel 112 including a cylindrical vessel casing114 enclosing an interior volume 116 of the vessel. In the interiorvolume is disposed a static flow restricting device 118, e.g., includingan array of capillary tubes arranged in parallel to one another, throughwhich fluid from the interior volume 116 can flow along a flow pathincluding static flow restricting device 118, auxiliary fluid reservoir120, flow conduit 122, flow modulating device 124, e.g., a selectivelyactuatable valve element such as a vacuum actuated dispensing checkvalve, and discharge conduit 126. The discharge conduit 126 deliversfluid to valve head 128 containing a valve element that is translatablebetween fully open and fully closed valve positions by the automaticvalve actuator 130, which is operated by control signals transmitted insignal transmission line 132 to such actuator from the CPU 134.

The valve head 128 of the vessel 112 includes a discharge port coupledto fluid discharge line 142 through which fluid is flowed to thedownstream fluid-utilizing facility 158, which may for example comprisean ion implanter, or a vapor deposition chamber, e.g., a chemical vapordeposition chamber or an atomic layer deposition chamber, of asemiconductor manufacturing facility.

In the fluid utilizing facility, the fluid supplied from fluid dischargeline 142 is utilized, and in the specific embodiment shown, the fluidutilization operation in facility 158 produces an effluent that isdischarged in effluent discharge line 160, and may be passed to anabatement facility (not shown) for abatement of the contaminantstherein.

A fluid pressure regulator 136 can be provided in discharge line 142 tocontrol the pressure of the fluid supplied by the fluid supply vessel.Discharge line 142 also contains a pressure transducer 138 joined insignal transmission relationship via signal transmission line 140 to thecentral processor unit (CPU) 134. Further contained in discharge line142 is a mass flow controller 154 joined in signal transmissionrelationship via signal transmission line 156 to CPU 134.

The fluid supply and utilization system shown in FIG. 3 employs bufferreservoirs 120 and 150 to provide additional fluid supply capability toaccommodate endpoint conditions that would otherwise involve a suddenonset drop in delivery pressure of the fluid being supplied, in theabsence of such buffer reservoirs.

The buffer reservoirs in the FIG. 3 system include auxiliary fluidbuffer reservoir 120 disposed in the interior volume 116 of vessel 112,between the capillary flow control device 118 and conduit 122. Thebuffer reservoir 120 thereby provides an additional volume of fluid fordispensing when the vessel is otherwise in an endpoint condition in itsoperation. The buffer reservoir 120 may be formed of a metal or othersuitable material or fabrication, and provides sufficient volume forbuffering of the flow of fluid from the vessel, in order to smooth therapid change (decrease) in fluid flow at the endpoint condition.

In addition to such internal buffering reservoir, the FIG. 3 systemincludes an external buffering reservoir 150, coupled with the dischargeline 142 by flow line 144 containing flow control valve 146. The flowcontrol valve 146 is joined in signal-receiving relationship with CPU134 via signal transmission line 148, whereby CPU 134 can transmit acontrol signal in signal transmission line 148 to the flow control valve146 for opening of same at the endpoint condition, to provide additionalfluid supply and thereby extend operating time to permit changeover orchange-out of the depleted fluid supply vessel, so that it is removedfrom service.

As shown, the CPU 134 is joined by respective signal transmission lines132, 140, 148 and 156, to valve head valve controller 130, pressuretransducer 140, flow control valve 146 and mass flow controller 154, sothat the CPU receives signals from pressure transducer 138 in signaltransmission line 140 and signals from mass flow controller 154 insignal transmission line 156. The CPU may be programmably arranged toutilize such signals to produce outputs that are transmitted in signaltransmission lines 132 and/or 148, to modulate the valve controller 130and/or flow control valve 146, to control the flow of fluid being passedto fluid-utilizing facility 158 in discharge line 142.

It will be recognized that pressure regulator 136, pressure transducer138 and mass flow controller 154 may be used singly as well as incombination with one or more of such elements, as may be desirable in agiven application of the fluid supply and utilization system.

Thus, the FIG. 3 system could be utilized with only pressure regulator136, with only pressure transducer 138, or with only mass flowcontroller 154, in various embodiments, and two or more of such elementsmay be used in other embodiments of such system as compositely shown inFIG. 3.

In one embodiment of the generalized system shown in FIG. 3, the outputsignal from mass flow controller 154 transmitted to CPU 134 in signaltransmission line 156 includes a proportional-integral-derivative (PID)signal from the mass flow controller, with such PID signal beingprocessed by the CPU to determine endpoint condition of the fluid supplyvessel 112.

In this respect, the delivery pressure of fluid supplied from vessel 112will rapidly change at an “inflection point” of the delivery pressurevs. time curve. Such inflection point change can be detected bymonitoring the PID output of mass flow controller 154, and utilized todetermine an endpoint condition of the fluid supply vessel, and initiateresponsive action, such as terminating flow of the on-stream vessel andswitching the process system over to a fresh vessel, or actuating thesupply of fluid from buffer reservoir(s) of fluid to extend operationprior to termination and/or switchover from the depleted vessel to afresh vessel. The CPU therefore may be arranged for monitoring,utilizing such PID output signal from the mass flow controller toresponsively modulate the fluid supply system.

In this respect, it is noted that the PID output monitoring of the massflow controller may be utilized to supply fluid from fluid supplyvessels operated under constant flow delivery conditions, as well aswith supply vessels operated in accordance with various duty cycles, inwhich fluid supply vessels are utilized to intermittently deliver fluidto a fluid-utilizing facility.

For example, a fluid supply vessel utilizing capillary flow control maybe operated in a duty cycle in which the vessel is in a fluid deliveringmode for 10 minutes followed by an off-line state of 10 minute duration,wherein such 10 minute on/10 minute off cycle is repetitively carriedout. In such circumstance, the PID signal profile of the mass flowcontroller, or the mass flow profile itself, may change with eachsuccessive on-stream segment of the duty cycle. Accordingly, the CPU maybe arranged to monitor such progressive changes and to utilize same indetermining the endpoint condition, or otherwise to control supply offluid in the fluid supply system.

The CPU, as utilized in various implementations of the fluid supplysystem of the present disclosure, may be arranged to store reference orbase line profiles for any of the operating parameters or variables ofthe fluid supply system, and to utilize monitoring of such parameters orvariables, to determine endpoint of the fluid supply vessel, bycomparison to the corresponding reference profile parameters or values.In such manner, a reference profile may be utilized to govern systemoperation in response to dynamically monitored process conditions,outputs of system components, etc.

FIG. 4 is a graph of delivery pressure, at constant flow conditions, asa function of time, for an illustrative fluid supply vessel utilizingcapillary-assisted flow control, in which the graph shows the gradualincrease and sudden onset drop in delivery pressure of the fluid beingsupplied as the vessel nears or reaches an endpoint condition. Thedelivery pressure curve, as shown, has an inflection point A, at whichthe delivery pressure is at a maximum value, and subsequently there is asteep drop in delivery pressure, as the vessel rapidly progresses to anexhausted state. This process characteristic can be usefully employed byappropriate monitoring of the delivery pressure, or other variables inthe process system showing similar inflection point characteristics atthe endpoint condition of the fluid supply vessel, so that the abrupttransition of the monitored characteristic or parameter (correspondingin FIG. 4 to the delivery pressure behavior about point A) is detectedand utilized to initiate action that is appropriate to the endpointcondition. This monitoring may involve determination of rate of changeof delivery pressure, integration of the delivery pressure curve, orother operations that identify and generate a response to the endpointcondition. Thus, the endpoint can be selected as the condition at theinflection point A on the delivery pressure curve, or at the conditionat which the supply vessel pressure is equal to the set point pressurefor dispensing, or at any other selected point on the delivery pressurecurve before or after point A on such curve.

The disclosure in another aspect relates to a fluid supply system,comprising a fluid supply vessel having an interior volume for holdingfluid, first flow circuitry in the interior volume arranged to controlflow of fluid during supply of fluid from the vessel, said first flowcircuitry including a static flow restricting device and a selectivelyactuatable valve element, and a second flow circuitry coupled with thevessel for discharging fluid therefrom, wherein the system comprises atleast one of the following elements:

-   -   (i) a buffering reservoir in the interior volume of the vessel,        coupled with the first flow circuitry, arranged to hold fluid        for buffering release thereof to the first flow circuitry;    -   (ii) a buffering reservoir exterior of the vessel, coupled with        the second flow circuitry, arranged to hold fluid for buffering        release thereof to the second flow circuitry;    -   (iii) a pressure regulator arranged to regulate fluid pressure        in the second flow circuitry;    -   (iv) a pressure transducer arranged to monitor fluid pressure in        the second flow circuitry; and    -   (v) a mass flow controller arranged to control mass flow of        fluid in the second flow circuitry        wherein when any one or more of elements (ii)-(v) is comprised        in said system, the system may further optionally comprise a CPU        programmably arranged to receive at least one monitoring signal        from a device monitoring at least one characteristic of the        fluid supply vessel or a fluid dispensed therefrom to determine        an endpoint of fluid supply from the fluid supply vessel.

Such fluid supply system in one implementation can include mass flowcontroller (v), wherein an output signal from the mass flow controlleris utilized by the CPU to output a control signal to control fluidsupply in the system. The output signal from the mass flow controllercan for example comprise a PID output signal. In such implementation, orin other implementations, the CPU can be arranged to output a controlsignal to modulate a flow control valve on the vessel, e.g., in thevessel's valve head, or in the second flow circuitry, or otherwise toterminate flow in the first and/or second flow circuitry. Otherimplementations will readily suggest themselves, based on the disclosureherein, in which the CPU is arranged to control, to effectuate atransition of the system to accommodate the endpoint condition of thefluid supply vessel, or otherwise to control fluid supply in the fluidsupply system.

In the fluid supply vessel in such illustrative implementations, thestatic flow restricting device can be of any suitable type, and can forexample comprise one or more capillary type or flow throttling passages,and the selectively actuatable valve element can comprise a vacuumactuated valve, or alternatively, the fluid supply vessel can beotherwise constituted and arranged as variously described herein.Additional implementations will readily suggest themselves, based on thedisclosure herein.

The number of capillaries in various embodiments of the disclosure canbe 8 to 10 or more, e.g., from 8 to 50, from 10 to 40, from 12 to 38,from 15 to 35, or other number of capillaries. The capillaries can be0.25 millimeter or more in internal diameter, e.g., from 0.25 to 5millimeters, from 0.30 to 4 millimeters, from 0.4 to 3.5 millimeters,from 0.5 to 3.0 millimeters, or other suitable size. The length of thecapillaries can be 3.5 inches in length or more, e.g., from 3.5 to 20inches, from 4 to 10 inches, from 4.5 to 8 inches, from 5 to 7.5 inches,or other suitable length. The fluid supply system fluid dispensing flowrate can be from 250 to 1000 sccm or more, e.g., from 250 to 900 sccm,from 300 to 850 sccm, from 350 to 800 sccm, from 400 to 750 sccm, orother suitable flow rate.

While the disclosure has been has been set out herein in reference tospecific aspects, features and illustrative embodiments, it will beappreciated that the utility of the disclosure is not thus limited, butrather extends to and encompasses numerous other variations,modifications and alternative embodiments, as will suggest themselves tothose of ordinary skill in the field of the present invention, based onthe disclosure herein. Correspondingly, the invention as hereinafterclaimed is intended to be broadly construed and interpreted, asincluding all such variations, modifications and alternativeembodiments, within its spirit and scope.

What is claimed is:
 1. A method of determining an endpoint of a fluidsupply process, the method comprising: selectively establishing fluidflow from a fluid supply vessel; controlling fluid flow through a flowpassage disposed in an interior volume of the fluid supply vessel with astatic flow restricting device and a selectively actuatable valveelement upon establishing fluid flow; and monitoring at least onecharacteristic of the fluid supply vessel or a fluid dispensed therefromto determine the endpoint, wherein the static flow restricting deviceand the selectively actuatable valve element are arranged along the flowpassage.
 2. The method of claim 1, wherein static flow restrictingdevice comprises a device selected from the group consisting of: (i) onecapillary or flow throttling passage; (ii) two or more capillary or flowthrottling passages arranged in parallel along a portion of the flowpassage; and (iii) a restricted flow orifice.
 3. The method of claim 1,wherein the static flow restricting device is positioned at a positionselected from the group consisting of: (i) a position before theselectively actuatable valve element on the flow passage; (ii) aposition such that the selectively actuatable valve element ispositioned between the static flow restricting device and an inlet ofthe flow passage; (iii) a position after the selectively actuatablevalve element on the flow passage; and (iv) a position between theselectively actuatable valve element and an inlet of the flow passage.4. The method of claim 1, wherein the selectively actuatable valveelement comprises a vacuum actuated valve.
 5. The method of claim 1,further comprising comparing the monitored characteristic to a referencecharacteristic to determine the endpoint, wherein the characteristic isselected from at least one of: fluid flow duration, fluid flow rate,fluid pressure, fluid or vessel temperature and concentration of acomponent of the fluid.
 6. The method of claim 1, wherein the endpointis determined to have been reached when: a) a predetermined fluid flowrate has been detected; b) a predetermined fluid pressure has beendetected; c) a predetermined fluid flow duration has been detected; d) apredetermined amount of fluid has been supplied; e) a predeterminedchange in fluid pressure has been detected; f) a predetermined change influid flow rate has been detected; and/or g) a predetermined weight orchange of weight of the supply vessel and its contents has beendetected.
 7. The method of claim 1, further comprising passing the fluidflow from the fluid supply vessel to a fluid-utilizing apparatuscomprising an ion implantation apparatus.
 8. The method of claim 7,wherein the fluid comprises a fluid species selected from the groupconsisting of arsine, phosphine, boron trifluoride, boron trichloride,diboron tetrafluoride, diborane, hydrogen selenide, xenon difluoride,silane, polyalkylsilanes, organometallic reagents, fluorine (F2),hydrogen sulfide (H2S), germane (GeH4), and hydrido and alkylhydridospecies of Si, Ge, Sn and Sb.
 9. The method of claim 6, wherein: theendpoint predetermined fluid flow rate is in a range of from 0.1 to 5standard cubic centimeters per minute; the endpoint predetermined fluidpressure is in a range of from 0 to 760 torr; the endpoint predeterminedfluid flow duration is within a range of from 250 to 550 hours; theendpoint amount of supplied fluid is in a range of from 250 to 300grams; the endpoint change in fluid pressure is in a range of from 10%to 50% of steady state delivery pressure; the endpoint change in fluidflow rate is in a range of from 1% to 15%; and the endpoint change ofweight of the supply vessel and its contents is in a range of from 15%to 60% in relation to original weight of the fluid supply vessel andfluid therein.
 10. The method of claim 1, wherein the monitoringcomprises monitoring implanter beam current or ion source arc current inan implanter receiving fluid from said fluid supply vessel, to detect adrop in such current levels, as being indicative of the fluid supplyvessel approaching an endpoint state.
 11. The method of claim 1, whereinsaid monitoring and endpoint determination comprise use of a CPU havingstored therein a fluid discharge operational profile for the monitoredvariable(s), as a baseline profile from which actual monitoring data canbe assessed for deviations that indicate onset or achievement of apredetermined fluid-depleted state of the fluid supply vessel.
 12. Themethod of claim 1, further comprising accumulating fluid in one or morebuffer volumes within or outside the vessel, wherein fluid in saidbuffer volumes are arranged to be discharged after the endpoint tomaintain fluid flow, and wherein the buffer volumes are of sufficientcapacity to maintain fluid flow during switchover to a fresh fluidsupply vessel.
 13. An endpoint monitoring and control apparatus for afluid supply vessel in which fluid flow is controlled through a flowpassage disposed in an interior volume of the fluid supply vessel with astatic flow restricting device and a selectively actuatable valveelement upon establishing fluid flow, said endpoint monitoring andcontrol apparatus comprising a monitoring unit adapted to monitor atleast one characteristic of the fluid supply vessel or a fluid suppliedtherefrom and to generate an output signal, and a CPU operatively linkedin output signal receiving relationship to the monitoring unit, said CPUhaving stored therein endpoint condition information and responsive inreceipt of an output signal from the monitoring unit indicative of theendpoint condition to generate a control signal for use in terminatingfluid supply from the fluid supply vessel.
 14. The endpoint monitoringand control apparatus of claim 13, further comprising a control deviceoperatively linked in control signal receiving relationship to the CPUand responsive in receipt of the control signal to operate and terminateor assisting to terminate fluid supply from the fluid supply vessel. 15.The endpoint monitoring and control apparatus of claim 13, wherein theendpoint condition information stored in said CPU comprises at least onefluid discharge operational profile for a monitored characteristic ofthe fluid supply vessel, as a baseline profile from which actualmonitoring data can be computationally assessed by the CPU fordeviations that indicate onset or achievement of a predeterminedfluid-depleted state of the fluid supply vessel.
 16. A fluid supplysystem, comprising a fluid supply vessel having an interior volume forholding fluid, first flow circuitry in the interior volume arranged tocontrol flow of fluid during supply of fluid from the vessel, said firstflow circuitry including a static flow restricting device and aselectively actuatable valve element, and a second flow circuitrycoupled with the vessel for discharging fluid therefrom, wherein thesystem comprises at least one of the following elements: (i) a bufferingreservoir in the interior volume of the vessel, coupled with the firstflow circuitry, arranged to hold fluid for buffering release thereof tothe first flow circuitry; (ii) a buffering reservoir exterior of thevessel, coupled with the second flow circuitry, arranged to hold fluidfor buffering release thereof to the second flow circuitry; (iii) apressure regulator arranged to regulate fluid pressure in the secondflow circuitry; (iv) a pressure transducer arranged to monitor fluidpressure in the second flow circuitry; and (v) a mass flow controllerarranged to control mass flow of fluid in the second flow circuitry,wherein when any one or more of elements (ii)-(v) is comprised in saidsystem, the system optionally further comprises a CPU programmablyarranged to receive at least one monitoring signal from a devicemonitoring at least one characteristic of the fluid supply vessel or afluid dispensed therefrom to determine an endpoint of fluid supply fromthe fluid supply vessel.
 17. The fluid supply system of claim 16,wherein the system comprises a mass flow controller (v) and said massflow controller is arranged to output a PID output signal, and the CPUis arranged to output a control signal in response to the PID outputsignal from the mass flow controller, for control of fluid supply in thesystem.
 18. The fluid supply system of claim 17, wherein the static flowrestricting device comprises one or more capillary or flow throttlingpassages.
 19. The fluid supply system of claim 16, wherein theselectively actuatable valve element comprises a vacuum actuated valve.20. The fluid supply system of claim 16, wherein the selectivelyactuatable valve element comprises a vacuum actuated valve, and thestatic flow restricting device comprises from 8 to 50 capillaries, eachhaving an internal diameter of from 0.25 to 5 millimeters, a length offrom 3.5 to 20 inches, wherein fluid dispensing flow rate of the fluidsupply system is from 250 to 1000 sccm.